With the improvements to its quality and with the proliferation in the number of cameras installed, video surveillance is increasingly often being used as an evidence element in law. Consequently, it has to be incontestable. More generally, good practices in protecting the private lives of citizens and the sensitivity of certain scenes observed are making it necessary to limit access to the video-surveillance data only to authorized people. Given these conditions, the authorities are having to enact strict rules controlling access to the video-surveillance systems, and to recommend, often in vague terms, the implementation of suitable technical procedures.
Typically, the procedure in many countries stipulates that, in order to collect evidence intended for the legal system, a judiciary police officer has to go to the storage server (which is itself constructed according to the best practices in terms of security) to collect the evidence item by personally copying the desired sequences onto a non-rewritable physical medium.
The recent extension of the IP architectures (use of the Internet protocols) to the shot-taking and of the shared transmission means (wireless or wired) further increases the threats of intrusion into the transmission system and, more generally, of fraudulent manipulation so as to corrupt the data.
The current response among the operators responsible for defining the systems and the integrators who design them is to try to physically secure the complete transmission systems between cameras and storage and display means. This requires expensive private data links and often centralization of the storage which makes it possible to dispense with the need for a judiciary police officer to go to the storage server, and dispense with the technical medium that has to accompany him or her, whereas a distributed storage would be the best topology.
Even though this legal insecurity is now minimal, disputes by one of the parties concerning the authenticity of the evidence which might have been manipulated by source replacement, elimination of objects from the image, etc., will continue to occur given the major issues involved, such as the possibility of the information obtained on analyzing a black box after an aircraft disaster being compromised.
The adoption by the video-surveillance systems of network infrastructures is a recent development, and the technical developments are frequent and rapid. Since cost is often a decisive factor, security still generally appears only as a minimum option.
The techniques currently employed to enhance security are limited to watermarking (adding a watermark, invisible overlaid information, whose function is to guarantee that the data are not modified) when encrypting the data (with general-purpose algorithms) during recording. Still at the level of just the recorders, the digital signature technique has been proposed, but with no signature key management policy (IGC or PKI) and with no evidence server.
When the video-surveillance systems include links between nodes, these nodes themselves have a processing capability, the techniques applicable to digital communications, such as the creation of a virtual private network (known by the acronym VPN) are naturally applicable, but cover, for their protection, only the exchanges between the points concerned.
Moreover, in the field of administrative and financial transactions, which correspond to limited exchanges of data in a succession of short sessions, “trust platform” techniques have been developed and are implemented for the general public (secure payments, dematerialized tax declarations, etc.).